The present invention relates to a detergent composition for precision cleaning, which is effective for cleaning the surface of a substrate prior to forming an organic or inorganic thin film on the surface of the substrate, and further cleaning an organic resin layer formed on the substrate surface during, for instance, liquid crystal display (LCD) device production processes, as well as a cleaning method using the detergent composition.
A polymer film of a polyimide and the like applied onto the surface of a substrate during, for instance, LCD device-production processes is subjected to a rubbing treatment for liquid crystal-orientation. The rubbed polyimide surface should be treated by precision cleaning because of the presence of pieces of the polyimide film, a rubbing cloth, peeled pieces of human tissues or cells, oils and fats released therefrom, and the like adhered to the surface.
These polymer films have conventionally been washed using a solvent such as a freon or isopropyl alcohol (IPA) or pure water or using a nonionic surfactant. However, the cleaning with the solvent suffers from problems of low safety to environment and high flammability. In addition, pure water does not show a sufficient detergency, while the cleaning using a combination of a nonionic surfactant and pure water is attended by such a bad effect that the yield is substantially reduced due to the surfactant remaining on the surface of the polyimide film. For this reason, there has increasingly been desired for the development of a surfactant which hardly remains on the surface of such a film to thus improve the yield and which can ensure high detergency.
For instance, Japanese Un-Examined Patent Publication (hereinafter referred to as "J.P. KOKAI") No. Hei 3-62018 proposes a method comprising ultrasonically cleaning the surface of a substrate with pure water to thus simultaneously obtain a stable pretilting angle in addition to an excellent cleaning effect, but the detergency of the method does not satisfy the degree of cleanliness recently required.
In addition, J.P. KOKAI No. Hei 3-81730 proposes a method for cleaning such a polymer film surface by scrubbing the surface with, for instance, a sponge, but it is difficult to completely eliminate the dust-generation during the scrubbing operation and it is not expected to obtain an effect of cleaning fats and oils released from peeled pieces of human tissues or cells.
Moreover, J.P. KOKAI No. Hei 5-264942 proposes a method for cleaning such a polymer film surface with pure water which also permits the cleaning off of an agent for enhancing the adhesion of the polymer film in addition to the residues present on the surface after rubbing operations by the employment of special process designed in such a manner that the surfactant play the role of the prevention of re-adhesion of the residues. However, there is a limit in the ability of water to peel off the residues from the surface.
Furthermore, J.P. KOKAI No. Hei 4-170500 proposes a detergent composition for cleaning LCD cells which comprises a nonionic surfactant as a principal component. However, this proposal relates to a finish-cleaning of an LCD cell after the production thereof and therefore, the purpose of this method and the effects thereof are different from those of the present invention.